mirror of
https://github.com/criyle/go-sandbox.git
synced 2025-11-04 14:49:53 +08:00
278 lines
7.4 KiB
Go
278 lines
7.4 KiB
Go
package tracer
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import (
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"runtime"
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"time"
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"github.com/criyle/go-judger/types/specs"
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unix "golang.org/x/sys/unix"
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)
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// MsgDisallow, Msghandle defines the action needed when traped by
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// seccomp filter
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const (
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MsgDisallow int16 = iota + 1
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MsgHandle
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)
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// Trace traces all child process that created by runner
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// this function should called only once and in the same thread that
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// exec tracee
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func Trace(handler Handler, runner Runner, limits specs.ResLimit) (result specs.TraceResult, err error) {
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var (
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wstatus unix.WaitStatus // wait4 wait status
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rusage unix.Rusage // wait4 rusage
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tle bool // whether the timmer triggered due to timeout
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traced = make(map[int]bool) // store all process that have set ptrace options
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execved = false // store whether the runner process have successfully execvd
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pid int // store pid of wait4 result
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sTime = time.Now().UnixNano() // records start time for trace process
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fTime int64 // records finish time for execve
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)
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// ptrace is thread based (kernel proc)
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runtime.LockOSThread()
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defer runtime.UnlockOSThread()
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// Start the runner
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pgid, err := runner.Start()
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handler.Debug("tracer started: ", pgid, err)
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if err != nil {
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handler.Debug("start tracee failed: ", err)
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result.TraceStatus = specs.TraceCodeRE
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return result, err
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}
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// Set real time limit, kill process after it
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timer := time.AfterFunc(time.Duration(int64(limits.RealTimeLimit)*1e6), func() {
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tle = true
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killAll(pgid)
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})
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// handler potential panic and tle
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// also ensure processes was well terminated
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defer func() {
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timer.Stop()
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if tle {
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err = specs.TraceCodeTLE
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}
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if err2 := recover(); err2 != nil {
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handler.Debug(err2)
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err = specs.TraceCodeFatal
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}
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// kill all tracee upon return
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killAll(pgid)
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collectZombie(pgid)
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result.TraceStat.SetUpTime = fTime - sTime
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result.RunningTime = time.Now().UnixNano() - fTime
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}()
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// trace unixs
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for {
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if execved {
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// Wait for all child in the process group
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pid, err = unix.Wait4(-pgid, &wstatus, unix.WALL, &rusage)
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} else {
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// Ensure the process have called setpgid
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pid, err = unix.Wait4(pgid, &wstatus, unix.WALL, &rusage)
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}
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if err != nil {
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handler.Debug("wait4 failed: ", err)
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return result, specs.TraceCodeFatal
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}
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handler.Debug("------ ", pid, " ------")
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status := specs.TraceCodeNormal
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if pid == pgid {
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// update resource usage and check against limits
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userTime := uint64(rusage.Utime.Sec*1e3 + rusage.Utime.Usec/1e3) // ms
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userMem := uint64(rusage.Maxrss) // kb
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// check tle / mle
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if userTime > limits.TimeLimit {
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status = specs.TraceCodeTLE
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}
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if userMem > limits.MemoryLimit {
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status = specs.TraceCodeMLE
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}
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result = specs.TraceResult{
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UserTime: userTime,
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UserMem: userMem,
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TraceStatus: status,
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}
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if status != specs.TraceCodeNormal {
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return result, status
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}
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}
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// check process status
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switch {
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case wstatus.Exited():
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delete(traced, pid)
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handler.Debug("process exited: ", pid, wstatus.ExitStatus())
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if pid == pgid {
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if execved {
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result.ExitCode = wstatus.ExitStatus()
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return result, nil
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}
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result.TraceStatus = specs.TraceCodeFatal
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return result, specs.TraceCodeFatal
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}
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case wstatus.Signaled():
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sig := wstatus.Signal()
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handler.Debug("ptrace signaled: ", sig)
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if pid == pgid {
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delete(traced, pid)
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switch sig {
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case unix.SIGXCPU:
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status = specs.TraceCodeTLE
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case unix.SIGXFSZ:
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status = specs.TraceCodeOLE
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case unix.SIGSYS:
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status = specs.TraceCodeBan
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default:
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status = specs.TraceCodeRE
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}
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result.TraceStatus = status
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return result, status
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}
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unix.PtraceCont(pid, int(sig))
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case wstatus.Stopped():
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// Set option if the process is newly forked
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if !traced[pid] {
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handler.Debug("set ptrace option")
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traced[pid] = true
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// Ptrace set option valid if the tracee is stopped
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err = setPtraceOption(pid)
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if err != nil {
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result.TraceStatus = specs.TraceCodeFatal
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return result, err
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}
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}
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// Check stop signal, if trap then check seccomp
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if stopSig := wstatus.StopSignal(); stopSig == unix.SIGTRAP {
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switch trapCause := wstatus.TrapCause(); trapCause {
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case unix.PTRACE_EVENT_SECCOMP:
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if execved {
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// give the customized handle for syscall
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err := handleTrap(handler, pid)
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if err != nil {
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result.TraceStatus = specs.TraceCodeBan
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return result, err
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}
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} else {
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handler.Debug("ptrace seccomp before execve (should be the execve syscall)")
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}
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case unix.PTRACE_EVENT_CLONE:
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handler.Debug("ptrace stop clone")
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case unix.PTRACE_EVENT_VFORK:
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handler.Debug("ptrace stop vfork")
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case unix.PTRACE_EVENT_FORK:
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handler.Debug("ptrace stop fork")
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case unix.PTRACE_EVENT_EXEC:
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// forked tracee have successfully called execve
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if !execved {
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fTime = time.Now().UnixNano()
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execved = true
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}
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handler.Debug("ptrace stop exec")
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default:
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handler.Debug("ptrace unexpected trap cause: ", trapCause)
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}
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unix.PtraceCont(pid, 0)
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} else {
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// check if cpu rlimit hit
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switch stopSig {
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case unix.SIGXCPU:
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status = specs.TraceCodeTLE
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case unix.SIGXFSZ:
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status = specs.TraceCodeOLE
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}
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if status != specs.TraceCodeNormal {
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result.TraceStatus = status
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return result, status
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}
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// Likely encountered SIGSEGV (segment violation)
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// Or compiler child exited
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if stopSig != unix.SIGSTOP {
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handler.Debug("ptrace unexpected stop signal: ", stopSig)
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}
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handler.Debug("ptrace stopped")
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unix.PtraceCont(pid, int(stopSig))
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}
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}
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}
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}
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// handleTrap handles the seccomp trap including the custom handle
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func handleTrap(handler Handler, pid int) error {
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handler.Debug("seccomp traced")
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msg, err := unix.PtraceGetEventMsg(pid)
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if err != nil {
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handler.Debug("PtraceGetEventMsg failed:", err)
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return err
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}
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switch int16(msg) {
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case MsgDisallow:
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ctx, err := getTrapContext(pid)
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if err != nil {
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handler.Debug("getTrapContext failed:", err)
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return err
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}
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syscallName, err := handler.GetSyscallName(ctx)
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handler.Debug("disallowed syscall: ", ctx.SyscallNo(), syscallName, err)
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return handler.HandlerDisallow(syscallName)
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case MsgHandle:
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if handler != nil {
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ctx, err := getTrapContext(pid)
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if err != nil {
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return err
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}
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act := handler.Handle(ctx)
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switch act {
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case TraceBan:
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// Set the syscallno to -1 and return value into register. https://www.kernel.org/doc/Documentation/prctl/seccomp_filter.txt
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return ctx.skipSyscall()
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case TraceKill:
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return specs.TraceCodeBan
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}
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}
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default:
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// undefined seccomp message, possible set up filter wrong
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handler.Debug("unknown seccomp trap message: ", msg)
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}
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return nil
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}
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// set Ptrace option that set up seccomp, exit kill and all mult-process actions
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func setPtraceOption(pid int) error {
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return unix.PtraceSetOptions(pid, unix.PTRACE_O_TRACESECCOMP|unix.PTRACE_O_EXITKILL|
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unix.PTRACE_O_TRACEFORK|unix.PTRACE_O_TRACECLONE|unix.PTRACE_O_TRACEEXEC|unix.PTRACE_O_TRACEVFORK)
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}
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// kill all tracee according to pids
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func killAll(pgid int) {
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unix.Kill(-pgid, unix.SIGKILL)
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}
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// collect died child processes
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func collectZombie(pgid int) {
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// collect zombies
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for {
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var wstatus unix.WaitStatus
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if _, err := unix.Wait4(-pgid, &wstatus, unix.WALL|unix.WNOWAIT, nil); err != nil {
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break
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}
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}
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}
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